Set a large heavy pot or Dutch oven over medium heat. Add the olive oil and let it warm for about 30 seconds.

Add the chopped onion, diced carrots, and diced celery to the pot. Sprinkle in 1/2 teaspoon of the salt and cook for 6 to 8 minutes, stirring often, until the vegetables look soft and glossy.

Add the sliced garlic, dried oregano, and red pepper flakes to the pot. Stir for 1 minute, until the garlic smells fragrant.

Add the tomato paste to the pot. Stir it for 1 to 2 minutes, until it darkens slightly and coats the vegetables.

Add the rinsed lentils to the pot. Stir for about 30 seconds so the lentils are coated with the tomato mixture.

Pour the crushed tomatoes and vegetable broth into the pot. Scrape the bottom of the pot with a wooden spoon so any browned bits mix into the stew.

Raise the heat to medium-high and bring the liquid to a full boil.

Lower the heat to low so the stew bubbles gently. Cover the pot partway with a lid and cook for 20 minutes.

Uncover the pot and stir the stew well, making sure the lentils are not sticking on the bottom.

Add the drained and rinsed chickpeas to the pot. Stir them into the broth.

Add the raisins to the pot. Cover the pot partway again and cook for 10 to 15 minutes more, until the lentils are tender and no longer chalky in the center when you bite one.

Stir the drained capers into the pot. Taste the stew and add the remaining 1 teaspoon salt and the black pepper, or more to taste if needed.